In many ways the soft-shell clam fishery exemplifies Maine’s rural micro-economies: small-scale, labor intensive, natural resource extraction in communities often dependent, because of few other economic alternatives, on the health of the resource base.

In 2013, soft-shell clams were Maine’s third largest fishery and worth approximately 16 million dollars—significant to the local economy, but not an important fishery outside the region.

Clammers use short-handled 4-6 tined rakes or hoes to dig down to the 2-4 inch clams that they harvest

That’s why it was curious that Sea Pact, a coalition of North American seafood distributors, got together to support the soft-shell clam fishery in Maine. The obvious place for Sea Pact to invest would be in the sustainability of the product they buy. Long-term assured supply is really where the confluence of economic interests and ecological interests meet around sustainability. It would make sense if Sea Pact were getting together to ensure there will be tuna to buy in 10 years, but why Maine soft-shell clams?

The answer from Rob Johnson, managing director of Sea Pact was pretty straightforward: “There was a real need for this research and it seemed like it would have an impact. This project is unique in that it approaches improvements on an ecosystem level by addressing invasive predators, impacts of rising seawater temperatures, and enhancing wild and cultured clam populations. That is one of the nice things about the collaboration of Sea Pact- you can think and act a little outside your normal individual business sphere with a collective association of progressive seafood companies that are dedicated to improvement within the industry.”

A species, and an ecosystem under threat

The Gulf of Maine is a region that is seeing impacts of climate change unlike other ocean regions including temperature changes more significant than in other parts of the ocean.

A report released by NOAA in March of 2016 was quite clear in outlining the problem: “Temperature drives ocean ecosystems in the same way it drives weather patterns,” said Kevin Friedland, an oceanographer with the Center’s Ecosystem Assessment Program. “The report shows how water temperature change caused by climate warming is affecting ocean organisms in our part of the Atlantic—spawning and the transport of eggs, young animals, and their prey. Warming is changing the ecosystem, and will continue to do so in the decades ahead.” Read the full article >>

There appear to be two types of warming going on. We often hear the long-term gradual warming associated with climate change, but we are also seeing incidents of significant “bursts” of temperature rise. The summer of 2016 seems to be poised for a heating (or really a not cooling down) of the Gulf of Maine similar to the disastrous temperatures seen in the Gulf four years ago.

From a recent article in the Portland Press Herald:

During the winter of 2011-2012, unusually warm temperatures caused the gulf to never properly cool down, and things warmed further through the summer, sending shock waves throughout the ecosystem.

Lobstermen started catching mounds of newly shed lobsters in May, six weeks ahead of their usual schedule, creating a glut that threw off the overwhelmed Maritime Canadian processing plants that usually purchase most of these fragile soft-shells, which aren’t hardy enough for the live whole lobster trade. Prices fell so low that the processors eventually jumped in, buying up the glut of cheap Maine lobsters instead of local lobsters, prompting eastern New Brunswick lobstermen to blockade trucks of Maine lobsters to prevent them from unloading.

On Eastern Egg Rock, puffin chicks starved because their parents were unable to find appropriate food for them, while off Grand Manan Island, northern right whales failed to find swarms of the tiny, cold-dependent marine copeods they like to eat.
Meanwhile, the warmer water triggered an explosion in the population of green crabs, which proceeded to devour most of the clams in Freeport, Brunswick, Penobscot and other towns.

Brian Beal, a marine shellfish ecologist at the University of Maine at Machias and the Downeast Institute, said the overall mass of green crab went down as the Gulf of Maine cooled in 2014 to 2015, but there are still large numbers of them – they’re just smaller.

“If seawater temperatures increase quickly in the spring and summer like in 2012-2013, we could see another explosion in the larger ones later in the summer or early fall,” he said.

Chad Coffin of Freeport, president of the Maine Clammers Association, says that would be a disaster.

“Here in Casco Bay, the soft-shell clam industry has totally collapsed, and a return to water temperatures experienced in 2012 could spell doom for a rebound that clammers have pinned to juvenile clams,” he said. Read the full article >>

Where to start?

One of the biggest challenges in addressing large-scale problems like climate change and invasive species is determining where to start—can you fix the problem, can you mitigate the impacts of the problem, do you need to figure out how to adapt to the problem. That is where the Sea Pact grant came in.

The grant given by Sea Pact in 2014 was to help Downeast Institute work with clammers in the town of Freeport to conduct large-scale, manipulative experiments to test hypotheses involving predator exclusion and habitat modification designed to enhance locally the number of both wild and cultured “spat” (juvenile clams). “This fishery management, fisheries improvement, and aquaculture improvement project is designed to create a new mindset amongst clammers and local clam stewardship committees to think and see beyond traditional approaches to conserve the resource“ according to the grant request.

Dr. Beal told SeaWeb that the Sea Pact money has been able to support research to help identify what management methods and tools have potential to better protect the clams and what methods are less effective. Trapping green crabs does not seem to be a viable option so research has also identified ways to protect clams from the crabs with netting or other barriers. The issue is further complicated by a resident, non-invasive specie whose populations have increased along with the crab. The milky ribbon worm bores into clams from underneath so deterrents for crabs are usually ineffective for the milky ribbon worm.

The project continues to identify better management opportunities for soft-shell clams and they have also found that small-scale operations seem to work best ecologically and socially—the fishery has traditionally been made up of individuals dependent on themselves and their rake.

Fortunately, Maine allows for a mix of public and private leasing for clam fishing, allowing researchers to consider a variety of management options to reduce pressures on the soft-shell clams.

It is not clear how much this research will be able to help if 2016 does turn out to be particularly warm, but Sea Pact’s vision and support have given the soft-shell clam resource and the individuals, businesses, and communities dependent on it an opportunity to hopefully grow and thrive.

And the research is providing some hopeful results. Beal and his crew discovered an area with an astounding 1,400 clams per square foot underneath nets they had placed there. Outside of the nets, there were 0.4 clams per square foot.

Male clam spawning. Gametes of male and females are expelled through the exhalent siphon and into the water column where fertlization occurs and larval development proceeds for 10-20 days depending on seawater temperatures.

Photomicrograph of a 6-day old soft-shell clam larvae. The animal is about 100 microns across. It has a shell, and the large, dark object in the middle of the animal is its gut. The hairs to the left are cilia that beat regularly to propel it through the water column and to force phytoplankton cells towards its mouth.

Broodstock clams are held in tanks sandwiched between pieces of wire and rigid netting to keep pressure on the shells (valves) so that they do not gape and die. Adult soft-shell clams typically burrow 6-10 inches into the sediments, and the pressure surrounding them keeps the valves closed. We cinch the two sides of the “sandwich” together tightly, and can keep adult clams alive for years at a time. These “clam sandwiches” are placed into tanks that receive seawater and phytoplankton (food) and we warm the seawater gradually over a period of eight weeks from 35oF to 50oF. At that point, the clams are ready to spawn.

Once clams complete their planktonic (swimming) phase, they settle to the bottom. In the wild, this can be a variety of habitats. In the hatchery, we give them no substrate to settle onto except trays with fine mesh screening. Over a 2-month period, clams grow at a rate that depends on seawater temperature and our ability to feed them the cultured, single-celled phytoplankton. In this photo of clams on window screening the length of the clams averages about 2.5 mm, which is 20 times larger than when they first settled out from the plankton.

Culturing phytoplankton (microalgae) at the Downeast Institute represents about 65% of the activities surrounding the production of soft-shell clams. Here, four different species of algae are being raised to afford clams a mixed diet, which produces faster growing clams. It takes about three weeks to produce the quantities of microalgae seen in this photo.

Approximately 10,000 soft-shell clam juveniles (averaging about 3 mm) are placed into wooden trays lined with window screening, and taken to a protected cove near the shellfish hatchery. Clams that are placed in these trays in June will reach a size of one-half inch to 5/8ths of an inch by November. Clams are then overwintered at the facility and seeded the next spring onto flats all over the state of Maine.

These are clams that average about one-half inch that have been growing in the tray since June (photo taken in October). There are periwinkles (snails) that are placed into the trays in June along with the small clams. The snails feed on macroalgae that might foul the window screening.

Clams are seeded in the spring by hand in plots that are covered with predator-deterrent netting.

Clammers use short-handled tined rakes or hoes to dig down to the 2-4 inch clams that they harvest.

Clammers use short-handled 4-6 tined rakes or hoes to dig down to the 2-4 inch clams that they harvest

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